Our objective is to explore the basis for the frequent occurrence of autoimmune and neoplastic disorders in the same individuals, and to clarify the possible common hemopoietic and immunologic aberrations which may predispose to both these diseases. New Zealand Black (NZB) strain mice of different ages and NZB yields DBA/2 radiation chimeras will serve as experimental models. We have recently shown that such chimeras develop persistent and high levels of antinuclear antibody and subsequent NZB-like glomerulonephritis. This raises the question whether such chimeras also develop the high regenerative and hyperresponsive capacities of NZB hemopoietic tissues, and their propensity to develop lymphoreticular neoplasms. Transplantability of these additional NZB characteristics will be measured by humoral and cellular responses to exogenous antigenic stimuli, endogenous spleen colony formation after sublethal x-ray exposure, and the occurrence of lymphoreticular neoplasms in the chimeras. Use of grafts of different cellular composition including DBA yields NZB should clarify (1) the interdependence between the hemopoietic and immunologic abnormalities, (2) the relationship of these to the development of lymphoreticular neoplasms, and (3) the role of host environment in expression of these abnormalities. The various chimeras and intact NZB mice of different ages will be tested for susceptibility to induction of sarcomas by 3-methylcholanthrene, lymphomas after sublethal x-ray exposure, and leukemia following inoculation of Rauscher virus. Utilizing the changing pattern with age of abnormalities of the autoimmune NZB strain, and modifying the expression of these abnormalities in chimeras, should result in a better understanding of the relationship between neoplasia and the hemopoietic and immune systems.